1. Field of the Invention
The present invention relates to a autostereoscopic three-dimensional (3D) image display apparatus that provides 3D images, and more particularly, to a autostereoscopic 3D image display apparatus having a modified sub-pixel structure.
2. Discussion of Related Art
A conventional autostereoscopic three-dimensional (3D) image display apparatus separates viewing zones using an optical plate, such as a lenticular lens or a parallax barrier. In this case, an observer in an observation position sees each corresponding viewpoint image for each of left and right eyes. As a result, the observer sees a 3D image.
FIG. 1 is a conceptual view of a multi-view 3D image display apparatus to which a conventional parallax barrier is applied, according to the related art, and FIGS. 2A and 2B are front views for describing types of parallax barriers in the multi-view 3D image display apparatus according to the related art. That is, FIG. 2A illustrates a case where a vertical parallax barrier is applied, and FIG. 2B illustrates a case where an inclined parallax barrier is applied. Here, the parallax barrier that is a parallax separation unit may also use a lenticular lens.
A plurality of pixels are arranged on a display panel of the conventional multi-view 3D image display apparatus to which the conventional parallax barrier illustrated in FIGS. 1, 2A, and 2B is applied. Here, a single pixel has a structure including red, green, and blue (RGB) sub-pixels in a horizontal direction. As illustrated in FIGS. 1, 2A, and 2B, single pixels are arranged in a matrix form in horizontal and vertical directions.
Referring to FIG. 1, in order to implement 3D images, a parallax barrier is disposed on a front surface of the display panel on which single pixels are arranged. Alternatively, a lenticular lens instead of the parallax barrier may be disposed as a parallax separation unit, or linear light sources arranged on a rear surface of the display panel at uniform intervals may also be used.
A common viewing zone caused by the number of designed viewpoints is implemented in an optimal viewing distance (OVD) by an optical plate designed according to the width of a pixel and the number of viewpoints of a display. FIG. 1 illustrates an example in which the common viewing zone is formed according to six viewpoint design. However, in the conventional multi-view 3D image display apparatus, the quantity of crosstalk varies with the observer's horizontal position movement (position movement parallel to the display panel).
As illustrated in FIG. 2A, in the conventional autostereoscopic 3D image display apparatus in which a vertical parallax separation unit is applied to a flat display panel having a conventional stripe type RGB pixel structure, there is an advantage that crosstalk between adjacent viewing zones is small. However, there is a disadvantage that there is chromatic dispersion of viewing zones formed in the horizontal direction and thus it is difficult to implement a 3D image of right color. For example, referring to FIG. 2A, viewing zone 3 is formed only with a blue color. Also, since resolution is reduced only in the horizontal direction due to an increase in the number of viewpoints, it is difficult to implement 3D images having proper horizontal and vertical resolution ratios.
FIG. 2B illustrates a case where an inclined parallax barrier having an angle of inclination of the parallax barrier of 18.43 degrees (arcTan(1/3)) is applied. In this way, when the inclined parallax barrier is used, the above problem that occurs in the vertical parallax barrier can be solved. That is, since, referring to FIG. 2B, viewing zone 3 is formed with RGB colors, the problem of chromatic dispersion for each viewing zone can be solved. Also, a reduction in resolution of the 3D image caused by an increase in the number of viewpoints can be divided in the horizontal and vertical directions. However, in this way, when the inclined parallax barrier is used, crosstalk between adjacent viewing zones increases. Also, when the observer is out of the OVD, bright and dark stripes (Moire phenomenon) of a screen appears in the 3D image display apparatus such that the range of observation in which an optimal 3D image can be observed, is limited.
Hereinafter, a viewing zone formation shape in the OVD and the above problem will be described with reference to FIGS. 3 and 4 in more detail.
FIG. 3 is a graph showing a color dispersion and a viewing zone formation shape in the OVD of the 3D image display apparatus to which the vertical parallax barrier illustrated in FIG. 2A is applied. Referring to FIG. 3, when the vertical parallax barrier is applied, ideally, images in adjacent viewing zones do not overlap in the center of each view zone. That is, in an ideal case, point crosstalk is 0 . For example, in FIG. 3, crosstalk in the center (in a position of a left vertical dotted line) of viewing zone 6 is 0 . However, when the observer is out of the center of the view zone, crosstalk with adjacent viewing zones increases rapidly, and brightness in the viewing zones is not uniform. For example, maximum crosstalk occurs in a point where two adjacent viewing zones cross. Furthermore, when the vertical parallax barrier is applied, an RGB color dispersion effect is shown in the horizontal direction, which means that it is difficult to implement proper colors of the 3D images.
FIG. 4 is a graph showing a viewing zone formation shape in the OVD of the 3D image display apparatus to which the inclined parallax barrier illustrated in FIG. 2B is applied. Referring to FIG. 4, even in an ideal case (in a position of the center of each viewpoint), point crosstalk is larger than 0 . For example, crosstalk exists even in a position of a right vertical dotted line that is a position of the center of viewing zone 2. Furthermore, when the inclined parallax barrier is applied, an RGB color pixel is formed in an inclined direction. Thus, the problem of color dispersion is solved but a Moire phenomenon occurs in a depth direction out of the OVD.
FIGS. 5A and 5B are photos showing a Moire phenomenon that occurs in the conventional 3D image display apparatus to which the inclined parallax barrier is applied. In detail, FIGS. 5A and 5B are photos showing a Moire phenomenon that occurs when an angle of inclination of the parallax barrier is 18.43 degrees (arcTan(1/3)). FIG. 5A shows a case where a depth direction Z is 1300 mm (OVD position), and FIG. 5B shows a case where the depth direction Z is 2500 mm The Moire phenomenon occurs due to a geometrical interference effect between lattices of the parallax barrier and display pixels. Referring to FIG. 5B, black lines appear in the inclined direction for a predetermined period. In general, a Moire effect is not large in the OVD (in case of FIG. 5A). However, when the observer moves in the depth direction, Moire image patterns having different periods that vary with moved distances from OVD can be observed (in case of FIG. 5B). However, even when, at a particular angle of inclination smaller than arcTan(1/3), the observer is out of the designed OVD and moves in the depth direction, a full white image in which Moire is minimized, can be observed like in the OVD.
FIGS. 6 and 7 illustrate a display panel having a modified RGB sub-pixel structure designed to solve the problem of the Moire phenomenon. FIGS. 6 and 7 illustrate the display panel having a pixel structure in which R, G, and B pixels are alternately arranged in the same row in the horizontal direction, which is disclosed in Korean Patent Laid-open Publication No. 10-2005-0025935 . However, pixels in adjacent rows in the vertical direction are arranged cornerwise about 1/2. Since, in this way, arrangement of pixels is shifted to an adjacent row and the pixels are formed in a zigzag form, Moire is offset in the entire display screen so that an image can be displayed. Furthermore, even when the vertical lenticular lens is used as a parallax separation unit, a color dispersion characteristic for each viewpoint image can be offset, and the horizontal and vertical resolution reduction ratios can be adjusted. However, the pixel structure illustrated in FIGS. 6 and 7 cannot be used in horizontal RGB sub-pixel structure of the conventional stripe type, and only a parallax separation unit perpendicular to a particular sub-pixel structure can be used. FIG. 8 illustrates a display panel having a modified RGB sub-pixel structure designed to solve the above problem. FIG. 8 illustrates a 3D image display apparatus having an inclined pixel structure and a parallax separation unit disclosed in Korean Patent Laid-open Publication No. 10-2011-0065982 . In detail, RGB sub-pixels are arranged in an inclined vertical direction so as to offset the color dispersion characteristic for each viewpoint image. The sub-pixel structure is formed in a parallelogram form so that crosstalk between adjacent view zones is minimized, and the sub-pixel structure is formed so that an inclination of two sides of the sub-pixel is the same as that of the parallax barrier. However, this structure cannot be used in the conventional stripe type horizontal RGB sub-pixel structure, and in this structure, a desired effect can be achieved only in a parallax barrier having a predetermined angle of inclination in a particular sub-pixel structure.